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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Laboratory Investigation of Quarry Fines for Use in the Construction Industry

Filippidi, Antonia January 2022 (has links)
Quarry fines are by-products of the aggregate extraction and productionprocesses. Because such fine material cannot be marketed, it becomes aburden for the aggregate industry, resulting in stockpiles of financiallyunexploited material. Even though previous research has been focused onminimizing the generation of quarry fines, far too little attention has beenpaid to maximizing their utilization instead. The aim of this thesis is toinvestigate whether 0/2 mm and 0/4 mm quarry fines can be utilized asalternative materials in the construction industry, specifically in theunbound layer of a road or as filling against a bridge. The methodologyconsisted of four laboratory tests that investigated the water content,particle size distribution and percentage of filler content, optimummoisture content (OMC) and maximum dry density (MDD) relationshipas well as bearing capacity of the materials. The results show that theamount of filler content (<0.063 mm) can significantly impact thematerial’s water-holding capacity as well as its compaction capabilities.After comparing the bearing capacity measurements to the technicalrequirements of the Swedish Transport Administration, it was found thatthe 0/2 mm fits the necessary requirements for use in the unbound layerof either a flexible or rigid pavement but not as filling against a bridge.Further research is needed to determine the material’s relationship towater absorption and resistance to freezing and thawing cycles, as it isdifficult to assess its suitability for road construction solely on theseresults; however, despite its limitations, the study provides some valuableinsights into the potential applications of quarry fines.
72

Correlating Concrete Mix Design to Rheological Properties of Fresh Concrete

Daoud, Omar I. 11 1900 (has links)
Workability has traditionally been used as one of the measures for controlling concrete mixture proportioning. This metric has provided limits on the water content in the concrete mixture for given aggregate size and type. The slump test, which is commonly used as an assessment of workability, is not adequate for characterizing the flow behaviour / rheology of fresh concrete. Studies have shown that Bingham's rheological properties, namely yield stress and plastic viscosity, provide good description of the flow behaviour of fresh concrete. In this thesis, an experimental program was designed on the basis of factorial design to evaluate the method of Cement Association of Canada for designing and controlling concrete mixture. The variables included in the mix design are water-cement ratio, water content, coarse aggregate size, silica fume, slag and bulk volume of coarse aggregate. In addition, Neuro-Fuzzy network has been adopted to correlate the current mixture proportioning method to the rheological properties of concrete. The network was constructed using experimental data tested in this study. Such correlation allowed the determination of water-cement ratio, water content, fine aggregate and coarse aggregate from compressive strength, yield stress and plastic viscosity. / Thesis / Master of Applied Science (MASc)
73

The Impact of moisture and clay content on the unconfined compressive strength of lime treated highly reactive clays

Muhmed, A., Mohamed, Mostafa H.A., Khan, A. 06 September 2022 (has links)
Yes / This study aims to provide a thorough evaluation for the changes in the microstructure and evolution of strength of highly reactive clays that were treated with 7 % lime over a period of curing time as a function of the mixing moisture content. Three series of testing were carried out on specimens with 100 %, 85 % and 75 % of bentonite content and prepared with different moisture content of 10, 20, 30 and 40 % above the corresponding optimum moisture content. Specimens of 100 % bentonite were treated with 7 % of lime, compacted to achieve a predetermined dry unit weight and cured at temperatures of 20 OC and 40 OC for up to 28 days whereas the specimens with 85 % and 75 % of bentonite content were prepared by the addition of sand and were cured at 20 oC for up to 7 days. Unconfined Compressive Strength tests and Scanning Electron Microscopy were conducted to observe the strength and the microstructural changes resulting from increasing mixing moisture content. California Bearing Ratio and Resilient Modulus were correspondingly determined based on correlations with the Unconfined Compressive Strength. The failure pattern was also studied to better understand the ultimate behaviour of lime stabilised clays. The results revealed that the strength of treated bentonite increased with the increase in the moisture content up to 30 % above the corresponding optimum moisture content and with increasing the curing time and temperature. Nevertheless, substituting bentonite with sand on the specimen resulted in a significant reduction on the attained strength. Furthermore, the results of California Bearing Ratio and Resilient Modulus showed that values for both parameters are significantly enhanced with lime treatment. The microstructural analysis provided visual evidence to the improved strength in which the pozzolanic reaction was found to be significantly affected by the amount of moisture in the mixture. The results suggested that compacting lime treated expansive clays with moisture content moderately higher than the optimum moisture content would result in a significant enhancement to the attained strength over the period of curing.
74

The Effect of Clay Content and Iron Oxyhydroxide Coatings on the Dielectric Properties of Quartz Sand

Cangialosi, Michael Vincent 05 June 2012 (has links)
Dielectric constant is a physical property of soil that is often measured using non-invasive geophysical techniques in subsurface characterization studies. A proper understanding of dielectric responses allows investigators to make measurements that might otherwise require more invasive and/or destructive methods. Previous studies have suggested that dielectric models could be refined by accounting for the contributions of different types of mineral constituents that affect the ratio and properties of bound and bulk water. This study tested the hypothesis that the dielectric responses of porous materials are mineral-specific through differences in surface area and chemistry. An experimental design was developed to test the dielectric behavior of pure quartz sand (Control), quartz sand/kaolin clay mixtures and ferric oxyhydroxide coated quartz sand. Results from the experiments show that the dielectric responses of quartz-clay and iron oxyhydroxide modified samples are not significantly different from the pure quartz Control. Increasing clay content in quartz sands leads to a vertical displacement between fitted polynomials. The results suggest that the classic interpretation for the curvature of dielectric responses appears to be incorrect. The curvature of dielectric responses at low water contents appears to be controlled by unknown parameters other than bound water. A re-examination of the experimental procedure proposed in this study and past studies shows that a properly designed study of bound water effects on dielectric responses has not yet been conduct / Master of Science
75

Water repellency effects on liquid- and vapor-phase water exchange in soil and clay minerals

Chen, Jingjing 12 February 2019 (has links)
Drought conditions and wildfires can induce soil water repellency. Precipitation shifts are expected to exacerbate drought and wildfire in regions such as the southeastern United States, making it critical to understand how repellency affects water exchange processes in soil. The objectives of this dissertation were to 1) quantify the water vapor sorption dynamics of two clay minerals in which water repellency was induced; 2) identify if and for how long wildfires in humid hardwood forests induce water repellency, 3) evaluate if organic carbon content and hydrophobic functional groups explain actual and potential soil water repellency; and 4) understand how vertical position (i.e., depth) of water repellent layers affect infiltration processes. To meet these objectives, a laboratory test was first conducted examining water vapor sorption processes in water-repellent clay minerals. Next, a field study occurred in two forests that experienced wildfires in late 2016: Mount Pleasant Wildfire Refuge, Virginia, and Chimney Rock State Park, North Carolina, United States. Measurements include water drop penetration time, soil water content, and tension infiltration. Complimentary laboratory tests quantified potential soil water repellency, soil organic carbon content and hydrophobic functional groups. Results showed that water repellency inhibited water vapor condensation because of altered mineral surface potentials and decreased surface areas. Burned hardwood forest soils presented water repellency for > 1 year, though laboratory measurements presented different trends than in situ measurements. Total organic carbon content and hydrophobic functional groups correlated with soil water repellency measured in the laboratory but not the field. Soil water content was lower in burned than unburned soils, and negatively correlated with water repellency. Water repellency in the surface layers significantly reduced relative water infiltration rates, whereas subsurface water repellency did not, and water repellency persisted longer in sites with surface compared to subsurface water repellency. Finally, while the wildfires increased the occurrence of water repellency, they did not alter the underlying relationship between relative infiltration and surface water repellency. Altogether, this study provided new insight into water repellency effects on water partitioning at soil-atmosphere interfaces, and presented evidence of soil and hydrological changes induced by wildfires in humid hardwood forests. / PHD / Rising temperatures and shifting precipitation patterns that result from global climate change have the potential to induce long-term droughts, which may induce soil water repellency, as can wildfires that become more prevalent and damaging. Water repellency can alter the physical, chemical, and hydraulic properties of soil. These alterations may drive soil erosional processes and increase the mobility of surface-bound pollutants with the potential to reduce water quality and degrade down-gradient aquatic ecosystems. Thus, it is critical to understand how water repellency affects water movement in and through soils. Despite several decades of research towards this topic, some critical questions still remain. For example, how does water repellent soil influence water characteristics in the vapor phase (which is increasingly important under drought conditions)? Do wildfires in humid hardwood forests cause soil water repellency? If so, how long does water repellency persist? Do water repellency measurements using field and laboratory techniques correspond to one another? How does the depth of water repellent soil layer(s) affect water movement? In order to solve this questions, several tests were conducted in both field and laboratory. The field experiments occurred within forested hillslopes that underwent varying degrees of burning during widespread wildfires that affected the Southeastern United States in late 2016. Choosing two forested locations, we measured actual water repellency, soil moisture, and infiltration in burned and unburned sites after wildfire, and took loose samples for laboratory tests. In the lab, we tested potential water repellency on air-dried soil samples, soil organic carbon content and hydrophobic substance percentage. We also conducted water vapor sorption experiments to quantify water vapor exchange in two types of water repellent minerals: kaolinite and montmorillonite. The results showed that water repellency can affect water exchange between the subsurface and the atmosphere, by both limiting water vapor sorption and reducing liquid water infiltration. Soil organic matter and composition correlate well with potential water repellency measured in the laboratory, though less so with actual water repellency measured in the field. Instead, soil water content provided a high and inverse correlation with actual water repellency. Finally, water infiltration rates were influenced by the vertical position (depth) of water repellent layers, with water repellency at the soil surface causing much reduced initial infiltration rates compared to water-repellent layers in the subsurface.
76

Validation of Spaceborne and Modelled Surface Soil Moisture Products with Cosmic-Ray Neutron Probes

Montzka, Carsten, Bogena, Heye, Zreda, Marek, Monerris, Alessandra, Morrison, Ross, Muddu, Sekhar, Vereecken, Harry 25 January 2017 (has links)
]The scale difference between point in situ soil moisture measurements and low resolution satellite products limits the quality of any validation efforts in heterogeneous regions. Cosmic Ray Neutron Probes (CRNP) could be an option to fill the scale gap between both systems, as they provide area-average soil moisture within a 150-250 m radius footprint. In this study, we evaluate differences and similarities between CRNP observations, and surface soil moisture products from the Advanced Microwave Scanning Radiometer 2 (AMSR2), the METOP-A/B Advanced Scatterometer (ASCAT), the Soil Moisture Active and Passive (SMAP), the Soil Moisture and Ocean Salinity (SMOS), as well as simulations from the Global Land Data Assimilation System Version 2 (GLDAS2). Six CRNPs located on five continents have been selected as test sites: the Rur catchment in Germany, the COSMOS sites in Arizona and California (USA), and Kenya, one CosmOz site in New SouthWales (Australia), and a site in Karnataka (India). Standard validation scores as well as the Triple Collocation (TC) method identified SMAP to provide a high accuracy soil moisture product with low noise or uncertainties as compared to CRNPs. The potential of CRNPs for satellite soil moisture validation has been proven; however, biomass correction methods should be implemented to improve its application in regions with large vegetation dynamics.
77

Hydrogen in nominally anhydrous silicate minerals : Quantification methods, incorporation mechanisms and geological applications

Weis, Franz A. January 2016 (has links)
The aim of this thesis is to increase our knowledge and understanding of trace water concentrations in nominally anhydrous minerals (NAMs). Special focus is put on the de- and rehydration mechanisms of clinopyroxene crystals in volcanic systems, how these minerals can be used to investigate the volatile content of mantle rocks and melts on both Earth and other planetary bodies (e.g., Mars). Various analytical techniques for water concentration analysis were evaluated. The first part of the thesis focusses on rehydration experiments in hydrogen gas at 1 atm and under hydrothermal pressures from 0.5 to 3 kbar on volcanic clinopyroxene crystals in order to test hydrogen incorporation and loss from crystals and how their initial water content at crystallization prior to dehydration may be restored. The results show that extensive dehydration may occur during magma ascent and degassing but may be hindered by fast ascent rates with limited volatile loss. De- and rehydration processes are governed by the redox-reaction OH- + Fe2+ ↔ O2- + Fe3+ + ½ H2. Performing rehydration experiments at different pressures can restore the water contents of clinopyroxene at various levels in the volcanic systems. Subsequently water contents of magmas and mantle sources can be deduced based on crystal/melt partition coefficients. This thesis provides examples from the Canary Islands, Merapi volcano in Indonesia and the famous Nakhla meteorite. Using NAMs as a proxy for magmatic and mantle water contents may provide a very good method especially for planetary science where sample material is limited. The thesis’ second part focusses on analytical methods to measure the concentration of water in NAMs. Specifically the application of Raman spectroscopy and proton-proton scattering are tested. The hydrated mineral zoisite is thoroughly analyzed in order to be used as an external standard material. Polarized single crystal spectra helped to determine the orientation of the OH-dipole in zoisite. Further, Transmission Raman spectroscopy and a new method for the preparation of very thin samples for proton-proton scattering were developed and tested. The results provide new possibilities for the concentration analysis of water in NAMs such as three dimensional distribution and high spatial resolution.
78

[en] STUDY OF THE MEASURING METHOD OF THERMAL CONDUCTIVITY AND WATER CONTENT BY MEANS OF SPHERICAL GEOMETRY: APPLICATIONS ON AQUEOUS SOLUTIONS OF ETHANOL / [pt] ESTUDO DO MÉTODO DE MEDIÇÃO DE CONDUTIVIDADE TÉRMICA E TEOR DE ÁGUA POR MEIO DE GEOMETRIA ESFÉRICA: APLICAÇÃO EM SOLUÇÕES AQUOSAS DE ETANOL

JULIO DUTRA BRIONIZIO 16 September 2013 (has links)
[pt] A presente tese tem por objetivo o estudo teórico e experimental, seguindo as boas práticas metrológicas, de um método baseado em uma fonte esférica de calor para medição da condutividade térmica de líquidos, com foco em soluções aquosas de etanol, e posterior determinação do teor de água da substância. O estudo e o desenvolvimento de métodos de medição de condutividade térmica são essenciais em diversas aplicações de engenharia, visto que, em consequência das justificadas demandas atuais de economia e uso racional de energia térmica, a transferência de calor com a máxima eficiência possível é de extrema relevância. A medição do teor de água também é um relevante parâmetro em muitas áreas de pesquisa e nos setores industriais, pois a quantidade de água nas substâncias influencia vários processos físicos, químicos e biológicos. Contudo, a quantidade de equipamentos disponíveis no mercado para a medição de ambas as grandezas não é vasta. O método da esfera quente, em principio, é um método absoluto de medição da condutividade térmica, o que significa que o sensor pode fornecer um resultado sem ser calibrado. Porém, alguns parâmetros do modelo precisam ser analisados isoladamente ou obtidos por meio de calibração. Embora haja alguns estudos sobre este método, poucos têm os meios líquidos como foco principal. Ademais, tais estudos não correlacionam a condutividade térmica do material com o seu teor de água e nem realizam uma análise metrológica mais criteriosa, de modo a determinar minuciosamente as incertezas de medição. A aplicabilidade do método para medição da condutividade térmica e do teor de água das soluções analisadas mostrou-se bastante satisfatória, pois os resultados obtidos neste estudo apresentaram muito boa concordância com os valores propostos por vários pesquisadores e com as medições realizadas no Inmetro por outros métodos. / [en] The aim of this thesis is the experimental and theoretical study, following the good metrological practices, of a method based on a spherical heat source in order to measure thermal conductivity of liquids, focusing on aqueous solutions of ethanol, with later determination of the water content of the substance. The study and the development of measuring methods of thermal conductivity are essentials in several engineering applications, since as a consequence of the current justified demands on saving and rational use of thermal energy, the heat transfer with the maximum efficient as possible is of great relevance. The measurement of the water content is also a relevant parameter in several research areas and industrial sectors, since the quantity of water in the substances influences several biological, chemical and physical processes. However, the amount of equipment available on the market for the measurement of both quantities is not vast. The heated sphere method, in principle, is an absolute one for the measurement of the thermal conductivity, which means that the sensor may furnish a result without a calibration. Nevertheless, some parameters of the model need to be analyzed separately or obtained by means of calibration. Although there are some studies on this method, few of them have liquids as the main focus. Moreover, these studies do not correlate the thermal conductivity of the material with its water content, and they do not perform a more careful metrological analysis in order to determine the measurement uncertainties. The applicability of the method to measure the thermal conductivity and the water content of the analyzed substances proved to be satisfactory, because the obtained results of this study presented a very good agreement with the values proposed by several researches and with the measurements performed at Inmetro by other methods.
79

Conservação de sementes de maracujá-amarelo (Passiflora edulis Sims f. flavicarpa Deg.): interferências do teor de água das sementes e da temperatura do ambiente. / Conservation of yellow passion fruit (Passiflora edulis Sims f. flavicarpa Deg.) seeds: interference of water content and environment temperature.

Fonseca, Samara Camargo Lopes 02 July 2004 (has links)
As sementes de maracujá-amarelo perdem rapidamente o poder germinativo quando são arbitrariamente armazenadas; assim, buscando embasamento para a definição de alternativas tecnológicas voltadas à desaceleração da deterioração durante o armazenamento, o objetivo da pesquisa foi o de estudar, através de variações no teor de água das sementes e na temperatura do ambiente, o comportamento fisiológico de sementes de maracujazeiro. A experimentação, realizada entre julho de 2002 e agosto de 2003 no Laboratório de Análise de Sementes localizado na Escola Superior de Agricultura Luiz de Queiroz/ USP, foi conduzida com sementes de maracujá-amarelo (Passiflora edulis Sims f. flavicarpa Deg.) produzidas em Mogi Mirim/ SP a partir de polinização aleatória entre plantas da Série IAC 270. Após a retirada da mucilagem das sementes, foi determinado o grau de umidade inicial do lote e, paralelamente, obtida a amostra representante do tratamento com o maior teor de água estudado (31%); as sementes remanescentes foram submetidas à secagem, em estufa com circulação de ar a 30°C ± 3°C, para a obtenção dos demais tratamentos referentes aos teores de água desejados (27%, 21%, 17%, 11% e 7%). Posteriormente, os tratamentos, correspondentes aos diferentes graus de umidade, foram armazenados em câmaras com temperaturas controladas de 10°C, 15°C e 20°C. Antes do armazenamento, e após 35, 70, 105, 140, 175, 210, 245, 280, 315 e 350 dias, as sementes foram submetidas às avaliações da qualidade. De acordo com os resultados obtidos, a combinação do grau de umidade de 7% com a temperatura de 10°C supera as demais no favorecimento à manutenção do potencial fisiológico das sementes de Passiflora edulis Sims f. flavicarpa Deg. / Yellow passion fruit seeds quickly lose the germination capacity when erratically stored; thus, seeding grounds to define technological alternatives to delay deterioration during storage, the goal of this research was to study the physiological behavior of passion fruit (Passiflora edulis Sims f. flavicarpa Deg.) seeds through varied seed water content and environmental temperature. The experiment was conducted at the Seed Analysis Laboratory of the Escola Superior de Agricultura Luiz de Queiroz - USP, from July 2002 through August 2003, with yellow passion fruit seeds produced in Mogi Mirim/ SP, through random pollination among IAC 270 Series plants. Following seed mucilage removal, the initial moisture degree of the lot was determined and the representative sample of the treatment with the highest water content studied (31%) was obtained concurrently; the remaining seeds were dried in na air-circulating oven at 30°C ± 3°C to achieve other treatments regarding the intended water contents (27%, 21%, 17%, 11% and 7%). Further, the treatments - corresponding to different moisture levels - were stored in controlled-temperature chambers at 10°C, 15°C and 20°C. Previous to storage and 35, 70, 105, 140, 175, 210, 245, 280, 315 and 350 days later, the seeds were submited to quality assays. The results indicate that the combination between 7% moisture degree and 10°C temperature overcomes the remaining ones towards favoring the maintenance of the physiological potential of Passiflora edulis Sims f. flavicarpa Deg. seeds.
80

Desenvolvimento de metodologia para a determinação da mobilidade de água no solo / Development of a method to determine water mobility in soil

Engler, Marcela Prada de Campos 27 April 2007 (has links)
As características hidráulicas do solo têm uma importância fundamental relacionada à disponibilidade de água para as plantas e ao transporte de solutos no solo. O modelo bifásico ou "móvel-imóvel" presume que o teor de água no solo (θ) pode ser dividido em duas frações: uma fração móvel (θm) e uma outra imóvel (θim). Define-se mobilidade μ da água no solo como a razão θm/θ. Correlações entre as funções θ(h), K(h) e μ(h) são esperadas, uma vez que essas três propriedades são relacionadas com a mesma estrutura do sistema poroso do solo. O objetivo do presente trabalho foi apresentar uma hipótese correlacionando a função mobilidade com a de condutividade, e testá-la através de dados obtidos segundo uma metodologia de laboratório desenvolvida. O experimento foi realizado em Piracicaba, SP e em Braunschweig, Alemanha. Amostras indeformadas de cinco solos (Latossolo Vermelho-Amarelo, no Brasil e Orthic Luvisol, Stagno-gleyic Luvisol, Dystric Podzoluvisol e Gleyic Podzoluvisol, na Alemanha) foram coletadas para a determinação das propriedades hidráulicas de retenção e mobilidade da água no solo. O método utilizado para a determinação da mobilidade da água consistiu na aplicação de um volume de água contendo o íon Cl- como traçador (um "pulso hidráulico") à amostra de solo sob sucção com o objetivo de simular eventos de chuva ou irrigação, que promovem uma alteração hidráulica rápida no solo. A difusão do íon entre as frações móvel e imóvel foi considerada desprezível, uma vez que o pulso hidráulico foi aplicado em uma única parcela e diretamente no solo, tornando o processo relativamente rápido. Resultados obtidos nos cinco solos avaliados indicam a existência de uma correlação linear entre μ e o valor de K/(dK/dθ), conforme hipotetizado. Utilizando o sistema de equações de Van Genuchten – Mualem, μ(h) pode portanto ser estimado por parâmetros da curva de retenção. A metodologia proposta permitiu a determinação da mobilidade da água em amostras de solo sob condições laboratoriais. A mobilidade da água mostrou ser uma função do volume relativo (v) aplicado podendo a relação μ – v ser parametrizada pelo ajuste de uma equação simples, com apenas um parâmetro. Não foi possível averiguar a existência de uma relação empírica entre esse parâmetro e os parâmetros da equação de Van Genuchten, possivelmente em função do número pequeno de dados disponíveis. / Soil hydraulic properties are essential for the determination of plant water availability and solute transport into the soil. The biphasic or mobile-immobile model concept assumes the soil water content (θ) to be divided in two fractions: a mobile fraction (θm) and an immobile fraction (θim). Soil water mobility, μ is defined as the ratio θm/&#952. Relationships between θ (h), K(h) e μ (h) are probable since these properties are related to the same soil pore structure. The objective of this study was to test a hypothesis regarding a correlation between the mobility function and the hydraulic conductivity function, using a new developed laboratory method to determine soil water mobility. The experiments were conducted in Piracicaba, Brazil and in Braunschweig, Germany. Undisturbed soil samples were collected in five soils (Oxisol, in Brazil, Orthic Luvisol, Stagno-gleyic Luvisol, Dystric Podzoluvisol e Gleyic Podzoluvisol, in Germany) to determine hydraulic properties and soil water mobility. The method used to determine water mobility consists in a water volume with Cl- ion as a tracer ("hydraulic pulse") applied to a soil sample under suction, simulating a rainfall or irrigation event leading to abrupt hydraulic changes. The ion diffusion between the mobile and immobile water fractions was negligible as the hydraulic pulse was applied directly to the soil in a relatively short process. Results of five evaluated soils indicate the existence of a linear correlation between μ and K/(dK/d θ), confirming the hypothesis. Using the Van Genuchten – Mualem equation system, μ(h) can therefore be estimated by retention curve parameters. The proposed laboratory method allowed determining soil water mobility in soil samples under laboratory. Soil water mobility showed to be a function of the applied relative volume (v), while the relationship μ – v could be modeled by a simple, one-parameter equation, however, it was not possible to verify the existence of an empirical relation between this parameter and parameters from the Van Genuchten equation, possibly due to small number of available data.

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